Regulating roentgen-ray tubes



(No Model.) 4 M. P. RICE.

REGULATING ROENTGEN RAY TUBES.

No. 594,143. Patented Nov. 23, 1897.

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UNITED STATES PATENT Price.

MARTIN P. RICE, OF SCI-IENECTADY, NEW YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW YORK.

REGULA'I 'ING ROENTGEN-RAY TUBES.

SPECIFICATION forming part of Letters Patent No. 594,143, dated November 23, 1897.

Application filed July 1'7, 1897. Serial No, 64 L887. (No model.)

To aZZ whom it may concern:

Be it known that I,'MARTIN P. RIoE, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Regulating Roentgen-Ray Tubes, (Case No. 579,) of which the following is a specification.

My invention relates to Roentgen-ray tubes; and it consists of an improved method of regulating the vacuum in the tubes, so that it may be maintained at just the point most efficient in producing the rays.

It is well known that with vacuum-tubes used for producing Roentgen rays a certain critical exhaustion must be maintained. It cannot be permitted to go too high, because in that case the electrical resistance of the tube rises, and sparks may pass over the outside of the tube; nor can it go too low, for then, also, the rays are not generated. In the tubes first employed this was a source of considerable difficulty, and the production of the rays was more or less uncontrollable, operators simply taking advantage of the time when the screen appeared brightest. Several devices have been contrived for controlling the vacuum, the best known of these consisting of a small extension from the tube, in which is placed a volatile salt, such as hydrate of potassium. vWhen the vacuum rises too high, this salt may be volatilized by the application of heat, and its vapor serves to lower the vacuum in the tube. The action of this, however, is not automatic, and the judgment of the operator is necessary to make it successful. Devices have been put upon the market for adjusting the vacuum automatically, consisting, in general, in shunting a portion of the currentand using it to vaporize the volatile salt in the other arrangement referred to. This shunt-circuit includes, ordinarily, a spark-gap designed to offer more resistance to the current than the tube when the latter is working with normal vacuum. When the vacuum in the tube rises above normal, (which is its tendency in course of working,) the resistance also rises, and current crosses the spark-gap in the shunt in preference to passing through. the tube. The

shunted current is employed to volatilize the salt either directly or indirectly, and thus the vacuum is reduced to the normal point.

The arrangements just described are a great improvement over anything previously used; but there are objections to them. Sufficient current not being conducted across the shunt quietly to effect the regulation the vacuum in the tube gradually rises until the voltage at the spark-gap is sufficient to puncture the intervening layer of air. The sparks that pass are often noisy and generally annoying to the operator and the subject being examined, and they sometimes momentarily practically short-circuit the tube, so that a flickering screen is produced in the fluoroscope.

In my invention I overcome the difficulties above referred to by substituting for the spark-gap a high resistance in the shunt-circuit, conducting the current through it without disruptive discharges. I have found that for this purpose a liquid resistance was best, and the form in which I prefer to use it is a glass tube containing Water or other suitable liquid.

' In the accompanying drawings, Figure 1 is an arrangement embodying my invention, the source of current and its connections not being illustrated, as this part of the apparatus is well understood. Fig. 2 is a side elevation of the resistance.

A is the tube, of well-known form.

B B are the sparking terminals.

C C are line-wires.

D is the extension from the tube supposed to contain a small quantity of a suitable volatile salt, many kinds of which are well known.

E is a resistance in the shunt-circuit. I have shown this as a glass tube filled with water; but of course any other resistance liquidproper amount of resistance in the shunt-circuit.

In Fig. 2 I show a side elevation of the tube, one end e of which is turned up, so that the Waterwill stand in it. The wires of the shunt-' circuit may then be inserted without any mechanical connection. It is of course immaterial What size or shape of tube is employed; but I have found that the arrangement shown is a good one.

YVhat I claim as new, and desire to secure by Letters Patent of the United States, is

1. An automatic vacuum adjuster for Roentgen-ray tubes, consisting of a shuntcircuit including in the path of the current a volatile salt within the vacuum inclosure, and a high resistance in lieu of the usual sparkp- 2. An automatic vacuum adjuster for Roentgen-ray tubes, consisting of a shunt circuit including in the path of its current a volatile salt, and a resistance consisting of a tube filled with water or other liquid.

3. An automatic adjustable vacuum-tube having a chemical bulb and a shunt-circuit discharging through the bulb and presenting a continuous path of high resistance from terminal to terminal, without spark-gaps at any point exterior to the tube.

4.. In an automatic adjustable vacuum-tube, the combination of a vacuum-tube having a chemical bulb, a shunt-circuit forming a continuous high-resistance path uninterrupted by spark-gaps at any point exterior to the tube, and means whereby the current in the shunt regulates the vacuum in the tube.

In Witness whereof I have hereunto set my hand this 6th day of July, 1897.

MARTIN P. RICE.

Witnesses:

B. B. HULL, A. II. ABELL. 

